The nature of Earth’s first crust

• Published in: Chemical Geology
• Main Authors: Carlson, Richard, Garçon, Marion, O’neil, Jonathan, Reimink, Jesse, Rizo, Hanika
• Other Authors: Department of Terrestrial Magnetism Carnegie Institution, Carnegie Institution for Science, Laboratoire Magmas et Volcans (LMV), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS), University of Ottawa Ottawa, Department of Geosciences PennState, College of Earth and Mineral Sciences, Pennsylvania State University (Penn State), Penn State System-Penn State System-Pennsylvania State University (Penn State), Penn State System-Penn State System
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: Earth's first crust; short-lived isotopes; crust-mantle differentiation; planet formation; Archean geology; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; Canada; North Atlantic
• Online Access: https://uca.hal.science/hal-02344389; https://uca.hal.science/hal-02344389/document; https://uca.hal.science/hal-02344389/file/Carlson%20et%20al_ChemGeol_2019_Post-print.pdf; https://doi.org/10.1016/j.chemgeo.2019.119321

International audience Recycling of crust into the mantle has left only small remnants at Earth’s surface of crust produced within a billion years of Earth formation. Few, if any, of these ancient crustal rocks represent the first crust that existed on Earth. Understanding the nature of the source materials of these ancient rocks and the mechanism of their formation has been the target of decades of geological and geochemical study. This traditional approach has been expanded recently through the ability to simultaneously obtain U-Pb age and initial Hf isotope data for zircons from many of these ancient, generally polymetamorphic, rocks. The addition of information from the short-lived radiometric systems 146Sm-142Nd and 182Hf-182W allows resolution of some of the ambiguities that have clouded the conclusions derived from the long-lived systems. The most apparent of these is clear documentation that Earth experienced major chemical differentiation events within the first tens to hundreds of millions of years of its formation, and that Earth’s most ancient crustal rocks were derived from these differentiated sources, not from primitive undifferentiated mantle. Eoarchean rocks from the North Atlantic Craton and the Anshan Complex of the North China Craton have sources in an incompatible-element-depleted mantle that dates to 4.4-4.5 Ga. Hadean/Eoarchean rocks from two localities in Canada show the importance of remelting of Hadean mafic crust to produce Eoarchean felsic crust. The mafic supracrustal rocks of the Nuvvuagittuq Greenstone Belt are a possible example of the Hadean mafic basement that is often called upon to serve as the source for the high-silica rocks that define continental crust. Many, but not all, ancient terranes show a shift in the nature of the sources for crustal rocks, and possibly the physical mechanism of crust production, between 3.0-3.6 Ga. This transition may reflect the initiation of modern plate tectonics. Eoarchean/Hadean rocks from some terranes, however, also display compositional ...